This invention relates to a switch used in, for example, small electrically driven tools, and more particularly to a lock-off switch.
Various gun-shaped electrically driven tools are known. The grip of such a tool is provided with a switch having a trigger-shaped slider. The slider is normally kept in off-position. To drive a motor disposed in the tool, the slider is pulled by the forefinger into on-position. So long as the slider is held in on-position, electric power is kept supplied to the motor.
An accidental pulling of the trigger-shaped slider results in an accidental rotation of a cutter, which is very dangerous. Thus an accidental pulling of the slider should be avoided. To this end various lock-off switches have been invented. Each of these switches comprises a trigger-shaped slider and a lock means for locking the slider at off-position. The lock means releases the slider when a push shaft protruding from one side of a switch case is pushed. One known lock-off switch comprises a trigger-shaped slider and a push shaft. While held in a first position, the push shaft prevents a pulling of the slider. While kept in a second position, the push shaft can be moved perpendicularly to the axis of the tool so as to allow a pulling of the slider. Another known lock-off switch comprises a switch case, a trigger-shaped slider, a push shaft, a slightly bent leaf spring disposed in the switch case and a compression spring provided beside the leaf spring. The leaf spring is secured to the slider at one end, and its free end has a projection. While the slider is held in off-position, the projection is held in a hole made in a side of the case under an urging force of the compression spring, thereby preventing a pulling of the trigger-shaped slider. To allow a pulling of the slider, the push shaft is pushed to pull the projection out of the hole against the urging force of the compression spring.